ABSTRACT
OBJECTIVES: Chemoprophylaxis is recommended during pregnancy to reduce the risk of placental infection. However, in areas with increasing drug resistance, it can trigger selection of resistant parasites in the placenta and increase the frequency of placental malaria. The objective of this study was to analyse the selection of drug-resistant parasites in the placenta in an area where chloroquine was still recommended as prophylaxis. PATIENTS AND METHODS: We analysed the polymorphism of parasites from matched placental and venous blood samples at the time of delivery from women in Dakar. Polymorphism of the isolates was studied using nested PCR typing of MSA1 and MSA2 genes, and full sequence of PfCRT exon 2. RESULTS: Of 692 women recruited at delivery, 72 had placental malaria. Two Pfcrt exon 2 genotypes were found, and 86% of the placentas had monoallelelic CVIET infection compared with 39% that had peripheral blood infection. Mixed parasite populations of CVIET/CVMNK occurred in 53% of the peripheral blood samples but only in 7% of the infected placentas. This selection of CVIET in placenta was not related to a decreased polymorphism of the parasites, as a large diversity of MSA1 and MSA2 was found in both placenta and venous blood. This diversity confirms that a multiplicity of circulation isolates can occur at low parasite transmission. msp1 and msp2 genotyping revealed mostly distinct populations of parasites in venous and placental blood. CONCLUSIONS: These data suggest that, even in low transmission areas, diverse parasite populations can accumulate in the placenta during pregnancy despite strong selection at the PfCRT locus due to chemoprophylaxis with chloroquine.
Subject(s)
Drug Resistance , Gene Frequency , Malaria, Falciparum/parasitology , Membrane Transport Proteins/genetics , Placenta/parasitology , Plasmodium falciparum/genetics , Protozoan Proteins/genetics , Adolescent , Adult , Animals , Antigens, Protozoan/genetics , Blood/parasitology , Chemoprevention/methods , Child , Chloroquine/therapeutic use , DNA, Protozoan/chemistry , DNA, Protozoan/genetics , Female , Humans , Malaria, Falciparum/epidemiology , Merozoite Surface Protein 1/genetics , Plasmodium falciparum/isolation & purification , Polymerase Chain Reaction , Pregnancy , Pregnant Women , Senegal/epidemiology , Sequence Analysis, DNAABSTRACT
The impact of placental malaria in African urban areas is poorly documented. We therefore conducted a study during the rainy season in Dakar, an area with low malaria transmission. Two groups of delivering women were enrolled according to the detection of PfHRP2 in placental blood. Ten percent of the women were positive for parasites in the placenta, and microscopic examination showed, respectively, 17%, 22%, and 44% of past, acute, and chronic infection. The mean birth weight decreased drastically with the infection of the placenta (2,684 +/- 67 versus 3,085 +/- 66 g for controls), particularly with chronic infection. Chronic infection was not linked with parasiteamia in maternal venous blood. Seventy-six percent of positive women were anemic (46% of the controls). Severe anemia was also associated with chronic infection. Long-lasting infections are the most deleterious to mother and infant and are most likely associated with drug resistance of parasites.
